The Walking Dead Season 9 jumps to a future where Alexandria, Hilltop, Oceanside, and the Sanctuary are co-existing in a kind of harmony and using old technology to build something new. Still, it's still not really clear when The Walking Dead Season 9 takes place and exactly how much time has passed. Although, there are some clues viewers can use.
According to TVLine, the exact length of time between the end of TWD Season 8 and the beginning of Season 9 is 18 months. That's a year and a half, to put it another way. Actor Tom Payne, who plays Paul "Jesus" Rovia on The Walking Dead, confirmed the gap in the preview special. Does that make sense? Is it believable in the episode? Let's check that math. None of the changes are that drastic. Dedicate fans of the comic won't be too surprised to see Carol and Ezekiel together, or Maggie leading the community at Hilltop. All of these new arrangements were already in the works the last time fans saw these characters.
The biggest indicator of how much time has passed between Season 8 and Season 9 is the age of Judith Grimes as well as Hershel Rhee, Maggie and Glenn's baby. Judith seems about three in the promotional material, and in the Season 9 premiere she's carrying on full conversations while coloring. That's a big difference than when we last saw her. She's played again by twins Chloe and Sophia Garcia-Frizzi, not the older actress who portrayed a dream version of Judith in Carl's infamous "Old Man Rick" vision for the future.
In the Season 9 premiere, by this writer's own infant assessment, Maggie's baby looks to be about a year old. Around the middle of Season 8, fans deciphered from canon that Maggie was only two months pregnant. If she was rounding out her first trimester at the end of Season 8, and eighteen months have passed, this totally checks out, too. That puts Hershel at ten or eleven months old, tops. If all goes well, he'll probably celebrate his first birthday at the Hilltop surrounded by his new family! After the horror that was the war against Negan and the Saviors, a baby smooshing a cake is exactly what these survivors need.
There's actually a third toddler on The Walking Dead now. Aaron's adopted daughter Gracie, who by this math should be almost two, is mentioned but not seen in the Season 9 premiere. Who's going to open up the post-apocalyptic preschool? Carol can start up her defense classes again, in hopes that none of these children go the way of Lizzie. (Never forget.)
Also, presumably during these missing eighteen months, Morgan left the (literal) trash heap where he was living and joined the survivors on Fear The Walking Dead. For those who don't watch the spin-off series, Morgan's not planning on returning to Alexandria any time soon. Otherwise, all of your faves are here and re-building civilization together. They did a lot in just 18 months — marking roads properly, building machinery and transport vehicles. Carl would be very proud.
Hopefully, as Season 9 gets going, different clues will drop that fill in the gaps of what everyone has been up to in those missing 18 months. So far, it seems like not too much drama, but knowing this show... keep those fingers crossed.